Screw-blank-heading machine.



P.-L. ROBERTSON. SCREW BLANK READING MACHINE. APPLICATION PPPPPP EB. 111111 0.

1,003,657. Patented Sept.,19, 1911.

SciaEW-BnANK-HEADING MACHINE.

incense.

Specification. of Letters Patent.

Patented Sept. 19, 191i.

ttontinuation in part of application Serial No. 401,224,'fi1ed November 8, 1907. This application filed 'February 12, 1910. Serial No. 543,648.

To all whom it may concern:

Be it known that I, PETER LYMBURNER ROBERTSON, of the city of Hamilton, in the Province of Ontario, Dominion of Canada,

have invented certain new and useful Improvements in Screw-Blank-Heading Machines; and I do hereby declare that the same is a full, clear, and exact description of the same.

My invention relates particularly to cold process headers, and it has for its object to provide.tools for a machine of this type whichwill produce a blank having a noncrystallized head with a socket of effective depth. 1

It has been proposed to punch in the head of a screw blank a slot with closed ends and a slot in the form of a cross in plan view and triangular in longitudinal section. The defects in these methods are'that in punching the first mentioned slot the metal is not caused to fiow evenly, and an effective depth cannot be produced without the metal in advance of the punch, being crys-' tallized thus fatally weakening the screw at its neck, and the slot produced is too shallow to afford an effective hold for the .screw driver; while in punching the second mentioned slot the metal flows unevenly and the form produced does not afford an effective hold for the screw-driver.

The present machine embodies means adapted to form the head of a screw blank by punching a socket or recess in the end of a piece of wire, by means of a punch presenting a male die of square cross section and all the sides whereof are of equal area and converge at a very slight angle while the end converges sharply to a point. The punch is reversible and formed at both ends with male dies such as scribed. A bumper block of relatively softmetal is provided and has a chamber at one end,

' reference characters and such punch and block are set in a ham mer, the chamber in the bum er block accommodating the die on the inner endof the punch. For full comprehension, however of my invention reference must be had to the accompanying drawings, forming a part of this specification, in which simllar indicate the same parts and wherein Figure 1 illustrates the hammers and mat-rlx'and a part of the machine in which just 'decompletion of the second blow which completes the socket, thus filling the matrix to its full capacity and forming and facing the head; Fig. 4 is an enlarged detail view of the completed head; Figs. 5 and 6 are detail perspective views of the punch and bumperblocks; Fig. 7 is an enlarged detail sectional View of the male die; Fig. 8 is a detail face view of the male die. Fig. 9 is a side elevation partly 'in sectional View taken on line A A. Fig. 4. and'illustrating a complete screw.

The matrix 6, and first and second hammers c and d, respectively, are mounted and operated in the usual way, the second hammer carrying the punch e'which is reversible and presents at each end a male die f of square cross-section and all the sides whereof are of equal area and as before mentioned converge at a very slight angle, While the end converges at an angle of forty five (45") degrees and terminates in a point preferably of pyramidal. form. The bumper block 9 of relatively softer metal is located behind the-punch e and the chamber to accommodate the die on the rear side of the punch is indicated at 2', the opposite end of such bumper block being without opening of any kind and affording means whereby, upon the set screw j being loosened, and a pin being inserted through a hole .9 in the hammer the. block and punch can be driven out of the hammer when it is desired to reverse or exchange the punch when the die is worn or a socket of different dimensions is to be punched.

The knock-out-pin, indicated at h, is operated in the usual manner. 1

The best results are obtained by making the die, punch block, bumper block and the hammer carryingt-hem in substantially the proportions .ilhistrated, the advantages being that the die will not break off of the punch block as readily as itl would from the relatively large body of the hammer if formed thereon; while the bum er b lock being of relatively softer mater al acts as a. cushion, and the slight measure of play hetweenthe punch'and bumper blocks and i metal caused thereby is continued by the sides although to a less extent in proportion to the distance traveled, and, besides producing a head with practically perfect conoidal surface and flat face, forms a socket the uniform and converging walls of which insures so effective a connection between the screw and its driver that such screw may be carried upon the point of the driver, while a proper alinement of the two being maintained the danger of the driver slipping is completely obviated. After the punching of the socket and forming of the head thereby, the blank is threaded and the screw finished in the usual way.

This method of producing screws has many advantages over cold-process methods of forming screw-heads heretofore unknown, in that the metal displaced as the socket is formed fills the matrix without causing defective distortion or crystallization. This is owing to the uniform spreading of the metal laterally from all sides of the punch by its sharply converged pointand slightly converged sides; the object being to spread the metal uniformly throughout the space between the punch and the wall of the matrix, and avoid forcing it in front of the punch which would cause crystallization.

While I have described my method of producing the screw blank I do not herein claim same as such will form the subject matter of pyramidal form and also square in cross section.

2. In a screw heading apparatus, the combination with a matrix block having a perforation to accommodate the length of stock from which the screw is formed, of a punch carrying a die having a body portion and a pointed portion, the body portion being square in cross section, slightly converging toward the pointed portion and of a length less than the depth of the head of the screw being formed and the pointed portion being of pyramidal form and also square in cross section.

3. Ina screw heading apparatus, the combination with a matrix block having a perforation to accommodate the length of stock from which the screw is formed, of a punch carrying a die having a body portion and a pointed portion, the body portion being square in cross section and o a length less than its width and the pointed portion being of pyramidal form and also, square in cross section.

In testimony whereof, I have signed my name to this specification, in the presence of two subscribing witnesses.

PETER LYMBURNER ROBERTSON.

Witnesses:

WILLIAM P. MCFEAT, ARTHUR H. EVANS. 

